You could check the msn gaming zone or gamespy arcade, but really all you need to do is find somebody else who has the game, host a game (in game, choose multiplayer and host) and then give people your IP.
They choose join and type it in, and then they're set!
Sorry, but JK/MotS have no dedicated servers. Best played on a LAN if you can manage (good pings on the internet are 100-200 with 500 being probably the highest one could tolerate).
Check out http://www.jediknight.net/jkmag/
for some help with playing with mods.
Trail's Guide has help posted with hosting and joining too if my comments weren't helpful enough (it's also of course a great all-around Single Player resource). http://www.jediknight.net/trail/guide.html